1. Field of the Invention
The present invention relates to a liquid crystal display (LCD) backlight assembly, and more particularly, the present invention relates to a backlight assembly using different radiation angles of different light emitting diodes for low manufacturing cost, compact exterior and luminance efficiency.
2. Description of the Related Art
As display devices are used in everyday life, the liquid crystal display (LCD) has been gaining popularity. The LCD has a thin film transistor (TFT) panel which includes a pair of opposing substrates with a liquid crystal layer therebetween. The LCD also has a backlight assembly since the liquid crystal layer is not self-emissive. The backlight assembly is located behind the TFT panel to provide light to the liquid crystal layer. With light from the backlight assembly, transmittance of the TFT panel is controlled by arranging the liquid crystal molecules for each pixel.
The backlight assembly is classified into two groups according to the location of a light source, a direct light backlight assembly and an edge light backlight assembly. In the edge light backlight assembly, the light source is located at a lateral side of a light guiding plate (LGP) which is placed between the TFT panel and the light source. A linear fluorescent lamp has been mainly used as the light source, but point light sources such as a light emitting diode (LED) are also popular for a small LCD.
Being a semiconductor device, the merit of an LED lies in long lifetime, low power consumption and compact exterior. However, on the other hand, a LED has the demerit of limited light emitting angle which is called a light radiation angle. In an edge light backlight assembly, the LGP has a dark area close to a light incident area due to a limited light radiation angle of the LED and has low space efficiency for illuminating.
To improve the low efficiency, an increased number of LEDs or a widened radiation angle for each LED may be used. However, in order to widen the radiation angle for each LED, each of the LED packages must be altered raising the LED package price. Accordingly, an increased number of LEDs or widening radiation angle of each LED may lead to high manufacturing cost, high power consumption and a bulky exterior.